Three-body interactions and the elastic constants of hcp solid ⁴He

Area of Science:

• Condensed Matter Physics
• Quantum Solids
• Materials Science

Background:

• Hexagonal close packed solid ⁴He exhibits unique quantum properties at low temperatures.
• Previous theoretical models for elastic properties often used simplified approximations for zero-point motions.
• The influence of three-body interactions on these properties remained an area for refined investigation.

Purpose of the Study:

• To investigate the effect of three-body interactions on the elastic properties of solid ⁴He.
• To accurately calculate elastic constants, including bulk and shear moduli, using advanced simulation techniques.
• To compare simulation results with experimental data and previous theoretical findings.

Main Methods:

• Utilized variational path integral (VPI) Monte Carlo simulations for accurate zero-point motion treatment.
• Incorporated a perturbative approach for nonadditive three-body potentials.
• Calculated elastic constants (bulk modulus, C₀, C₆₆, C₄₄) across a range of molar volumes (7.88–20.78 cm³/mol) at 0 K.

Main Results:

• VPI simulations with three-body interactions significantly improved agreement with experimental bulk modulus.
• Non-negligible differences, up to 26.5%, were observed in pure shear and nonzero elastic constants at higher densities.
• Calculated elastic constants showed good to better agreement with experimental data compared to prior studies.

Conclusions:

• Three-body interactions are crucial for accurately describing the elastic behavior of solid ⁴He.
• VPI Monte Carlo simulations provide a more reliable method for studying quantum solids.
• The findings offer improved theoretical predictions for the mechanical response of solid ⁴He.